In 1919 a young Russian mathematician, Marcel Tolkowsky, wrote a Master thesis, Diamond Design, on the proportions for Round Brilliant Cut diamond. He systematically analyzed the optics of a diamond and estimated the best proportions for cutting round brilliant diamonds. This became the basis of what is now known as ‘The Ideal Cut’.
The above diagram shows the proportions of a diamond in Tolkowsky’s Ideal Cut.
But it has taken more than 50 years for diamond cutters to realize that the theorem put forward by Tolkowsky predicted a range of proportions and not just a single set of parameters. Tolkowsky was also aware that there was a trade-off between maximum brilliance and maximum fire that would result from varying combinations of crown and pavilion angles.
For those not in the diamond trade, it must be noted that a diamond cut is a design guide used for shaping a diamond. Cut does not refer to the shape (such as round brilliant, pear or oval) but the symmetry, proportioning and polish of a diamond. The cut will have a great impact on a diamond’s brilliance and will dictate the luminosity of it.
Today’s Ideal Cut follows closely those strict proportions of Tolkowsky’s original model with some changes as technology, notably laser cutting and CAD, improves on how a diamond is cut, taking into consideration the balance between best optical performance and the maximum retention of weight.